1. Field of the Invention
The invention concerns a device for needling of a nonwoven web.
2. Description of Related Art
The known device is used for consolidation and structuring of nonwovens. For this purpose, a nonwoven web is punctured by a number of needles, which are guided in an oscillating up and down movement. During the process, the needles are guided with an oscillating vertical movement, in order to consolidate the fiber material in the nonwoven web. The nonwoven web during this process is continuously moved forward with an advance, preferably executed by rolls. Since the needles are not smooth, but are provided with counter-hooks opened in the puncturing direction, filaments of the nonwoven are grasped during puncturing and reoriented in the nonwoven. Because of this, the desired felting and consolidation effect occurs in the nonwoven. In order not to obtain undesired deformations, which lead, for example, to warping or elongated hole formation in the needled material, during puncturing of the needles in the nonwoven web, because of advance of the nonwoven web, the needles are guided with a superimposed horizontal movement. In this case, the movement of the needles is aligned in the advance direction of the nonwoven web. To carry out a vertical movement and a superimposed horizontal movement of the needles, essentially two different drive variants are known in the prior art.
A generic device for needling of a nonwoven web is known from DE 197 30 532 A1, in which a needle bar is connected to a vertical drive to execute an up and down movement and to a horizontal drive to execute a back and forth movement. The horizontal drive is formed by two oppositely driven eccentric drives, which are formed from two parallel connecting rods and crankshafts connected to the connecting rods. The phase positions of the crankshafts are adjustable relative to each other, so that the horizontal stroke transferred by the connecting rods to a coupling element is adjustable in size. The horizontal movement is transferred from the coupling element directly to a bar support or through an intermediate coupling mechanism. The separate horizontal drive of the known device, however, requires complicated mechanisms, which results in insufficient stability and insufficient guiding of the needle bar, especially at higher passage speeds. Consequently, machine dynamic problems are to be expected when larger stroke frequencies are implemented with simultaneous stroke adjustment capability in the known device.
In a second variant of the drive technique for such devices, which is known, for example, from DE 103 55 590 A1, the vertical and horizontal movement is executed by a common drive. Here, two phase-adjustable crankshafts are used in conjunction with two connecting rods positioned obliquely relative to each other, whose connecting rod top ends meet at a point. Depending on the phase rotation of the crankshafts, a movement similar to an ellipse is obtained with variable horizontal and vertical stroke. Such concepts, however, have deficient speed stability and parallel guiding of the needle bar relative to the nonwoven web is also not possible.
In practice, however, there is an increasing desire to needle the nonwoven web with high speed and, if possible, variable horizontal stroke.
In order to generate the movement of a needle bar with separate vertical drive and horizontal drive, additional devices are known in the prior art, as disclosed, for example, in DE 196 15 697. Here, the horizontal drive is formed by an eccentric drive, which has a connecting rod cooperating with a crankshaft. The connecting rod acts with its connecting rod top end directly on a bar carrier, on whose bottom a needle bar is held. Such devices do permit higher passage speeds of the nonwoven web, but have the major drawback that the horizontal stroke is not variably adjustable.
Another device for needling of a nonwoven web is known from DE 100 43 534 A1, in which the bar carrier is formed by a pushrod guided in a pivot tube. The pivot tube is pivoted back and forth relative to a pivot axis. To this extent, the bar carrier is pivoted via a pivot drive relative to the pivot axis. The device as well as the pivot drive are therefore not appropriate for guiding the needle board or boards parallel to the nonwoven web.
It is now the task of the invention to modify a device for needling of a nonwoven web of the generic type, so that nonwovens can be needled in high quality at high passage speeds with variable stroke adjustment and high stroke frequencies.